BA INCEU60 ex-AMS can get you to HKG (via LHR and BKK) for circa GBP1450 J - currently available year round with a 60 day advance purchase requirement.
Business class on the BA777s which fly to BKK is, by all acounts very poor - certainly not a patch on QR. However if you fly direct to HKG and then take a side trip to BKK making sure you stay more than 24 hours you will get the same price, with the option of flying to and from Hong Kong on the BA A380 where business class is a lot better (albeit still a long way behind QR.
I'm not sure that you can book the BKK side trip on the BA website. But you can do a multi-flight search on Google flights: AMS-HKG-BKK-HKG-AMS with the HKG-BKK-HKG sectors being on CX or RJ and this should price up correctly. Then 'phone BA to make the booking.
You will of course need a positioning flight to AMS, and if you don't really relish a second visit to Amsterdam, book your final flight LON-AMS from LCY or LGW, so you get to collect your luggage at Heathrow, and then sadly miss the connection on to Amsterdam